BIOLOGY:SHORT NOTES
Cell specialization; is the process wherein “general” or
“common” cells evolve to form specific cells that have
specific functions.
The cell life cycle is composed of interphase(growth stage)
followed by mitosis or meiosis(division stage).
Cell specialization continues until adulthood, when the cells
(adult stem cells) divide to replace cells and worn-out tissues.
CELL SPECIALIZATION IN PLANTS
a. Root Hair Cells
1. Function: Absorb water and minerals from the soil.
2. Adaptations: They have long, thin projections that
increase the surface area for absorption. These cells lack
chloroplasts since they are located underground, where
there is no light for photosynthesis.
b. Xylem Cells
1. Function: Transport water and dissolved minerals from
the roots to the leaves.
2. Adaptations: Xylem vessels are made up of dead cells
that form long tubes. The end walls of these cells are
broken to allow water to flow freely, and their walls are
strengthened with lignin to provide support.
c. Phloem Cells
1. Function: Transport sugars and nutrients throughout
the plant.
2. Adaptations: Phloem vessels consist of living cells with
small holes in their end walls, allowing for the
movement of food products up and down the plant
d.Guard cells
1. Function: Guard cells surround the stomata (small
openings) on the surface of leaves and regulate gas
exchange and water loss. They control the opening
and closing of the stomata, which is crucial for
photosynthesis and transpiration.
2. Adaptations:
➢Cell Wall Structure: The inner walls of guard cells
are thicker than the outer walls. This difference
allows the cells to bend when they become turgid
(swollen with water), opening the stomata, and to
close when they are flaccid (losing water) .
➢Chloroplasts: Guard cells contain chloroplasts,
which may help in producing the energy needed for
their function .
e.Palisade Cells
1. Function: Palisade cells are located in the upper
part of the leaf and are primarily responsible for
photosynthesis, capturing light energy to
convert carbon dioxide and water into glucose
and oxygen.
2. Adaptations:
➢Shape and Arrangement: Palisade cells are
elongated and tightly packed, maximizing light
absorption. Their tall, thin shape allows light to
penetrate deeper into the leaf .
➢Chloroplast Density: These cells contain a high
number of chloroplasts, enhancing their ability
to perform photosynthesis efficiently
CELL SPECIALIZATION IN ANIMALS
1. Red Blood Cells
i. Function: Transport oxygen from the lungs
to body tissues and carry carbon dioxide back
to the lungs.
ii. Adaptations:
➢Biconcave shape increases surface area for
gas exchange.
➢Lack of a nucleus allows more space for
hemoglobin, the protein that binds oxygen.
2. Muscle Cells
i. Function:
Facilitate
movement
by
contracting and relaxing.
ii. Adaptations:
➢Elongated structure enables contraction.
➢High number of mitochondria provides
energy for movement through aerobic
respiration.
3. Neurons (Nerve Cells)
i. Function:
Transmit
throughout
the
electrical
impulses
body,
facilitating
communication between different body
parts.
ii. Adaptations:
➢Long axons allow signals to travel over
distances.
➢Dendrites
increase
surface
area
for
connections with other neurons.
4. Sperm Cells
i. Function: Transfer genetic material from the
male to the female during reproduction.
ii. Adaptations:
➢Flagellum (tail) enables swimming towards
the egg.
➢Contains enzymes in the head to penetrate
the egg’s outer layer.
5. Beta Cells (in the Pancreas)
i. Function: Produce and release insulin, a
hormone that regulates blood sugar levels.
Adaptations:
➢Specialized Organelles:
a. Ribosomes
and
Rough
Endoplasmic
Reticulum (RER): Beta cells have an
abundance of ribosomes and RER, which
are essential for synthesizing proteins,
including insulin.
b. Golgi Apparatus: This organelle processes
and packages the newly synthesized insulin
for secretion.
➢Granules:
a. Insulin Granules: Beta cells contain secretory
granules that store insulin. These granules are
released into the bloodstream in response to
rising blood glucose levels.
b. Cell Membrane Receptors:
➢Glucose Transporters: Beta cells have
glucose transporters (GLUT2) on their
membranes that allow glucose to enter the
cells. This is crucial for sensing blood sugar
levels.
➢Mitochondria:
a. High Mitochondrial Density: Beta cells have
numerous mitochondria to produce ATP
(adenosine triphosphate), which is necessary
for the energy-dependent processes involved
in insulin secretion.
➢Calcium Channels:
b. Voltage-Gated Calcium Channels: When
blood glucose levels rise, these channels
open, allowing calcium ions to enter the cell,
triggering the release of insulin granules